Today I Learned

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Elixir: Sandboxing an `iex` session

We can change the default .iex.exs file for another to be pre-loaded by iex using --dot-iex:

MIX_ENV=test iex --dot-iex .iex-sandbox.exs -S mix

This way we could create a rudimentary way to “protect” our existing database of changes on the iex session. Check this out:

# .iex-sandbox.exs
:ok = Ecto.Adapters.SQL.Sandbox.checkout(MyApp.Repo, ownership_timeout: 300_000)

This approach works for existing databases, so if the app we are working has a very difficult data setup then maybe this is the way to go. Although, making the db to hold data changes for as long as iex sessions are running it can be a bit too much in terms of db memory. Row & Table locks can definately be a problem as well.

Another important note is that we may have to call Sandbox.allow/3 if we need to call a GenServer or another process that touches the db.

The way to go

If we have a simpler data, with a nice seeds file, we’d be much better this way:

(export DB_NAME=my_app_sandbox && mix ecto.reset && iex -S mix)

Don’t forget to change our ecto config to use that ENV var.

Looking for help? At Hashrocket, we 💜 Elixir! From our many Elixir client projects, to sponsoring the Chicago Elixir Meetup, to the source code for this application, we are invested in this community. Contact us today to talk about your Elixir project.